Intermittent Travis failure #4 (flaky Pip)

gistfile1.txt

TASK: [app-test | install pip dependencies for running the unit and functional tests] *** 
failed: [localhost] => {"cmd": "/usr/local/bin/pip install -r /home/travis/build/freedomofpress/securedrop/securedrop/requirements/test-requirements.txt", "failed": true}
msg: stdout: Downloading/unpacking Flask-Testing==0.4.2 (from -r /home/travis/build/freedomofpress/securedrop/securedrop/requirements/test-requirements.txt (line 1))
  Running setup.py (path:/tmp/pip_build_root/Flask-Testing/setup.py) egg_info for package Flask-Testing
    
    warning: no previously-included files matching '*.pyc' found under directory 'tests'
    warning: no previously-included files matching '*.pyc' found under directory 'tests'
    warning: no previously-included files matching '*.pyc' found under directory 'docs'
    warning: no previously-included files matching '*.pyo' found under directory 'docs'
    no previously-included directories found matching 'docs/_build'
    no previously-included directories found matching 'docs/_themes/.git'
Downloading/unpacking mock==1.0.1 (from -r /home/travis/build/freedomofpress/securedrop/securedrop/requirements/test-requirements.txt (line 2))
  Running setup.py (path:/tmp/pip_build_root/mock/setup.py) egg_info for package mock
    
    warning: no files found matching '*.png' under directory 'docs'
    warning: no files found matching '*.css' under directory 'docs'
    warning: no files found matching '*.html' under directory 'docs'
    warning: no files found matching '*.js' under directory 'docs'
Downloading/unpacking pytest==2.6.4 (from -r /home/travis/build/freedomofpress/securedrop/securedrop/requirements/test-requirements.txt (line 3))
  Running setup.py (path:/tmp/pip_build_root/pytest/setup.py) egg_info for package pytest
    
Downloading/unpacking selenium==2.44.0 (from -r /home/travis/build/freedomofpress/securedrop/securedrop/requirements/test-requirements.txt (line 4))
Cleaning up...
Exception:
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/basecommand.py", line 122, in main
    status = self.run(options, args)
  File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/commands/install.py", line 278, in run
    requirement_set.prepare_files(finder, force_root_egg_info=self.bundle, bundle=self.bundle)
  File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/req.py", line 1197, in prepare_files
    do_download,
  File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/req.py", line 1375, in unpack_url
    self.session,
  File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/download.py", line 572, in unpack_http_url
    download_hash = _download_url(resp, link, temp_location)
  File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/download.py", line 433, in _download_url
    for chunk in resp_read(4096):
  File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/download.py", line 421, in resp_read
    chunk_size, decode_content=False):
  File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/_vendor/requests/packages/urllib3/response.py", line 240, in stream
    data = self.read(amt=amt, decode_content=decode_content)
  File "/usr/local/lib/python2.7/dist-packages/pip-1.5.6-py2.7.egg/pip/_vendor/requests/packages/urllib3/response.py", line 187, in read
    data = self._fp.read(amt)
  File "/usr/lib/python2.7/httplib.py", line 561, in read
    s = self.fp.read(amt)
  File "/usr/lib/python2.7/socket.py", line 380, in read
    data = self._sock.recv(left)
  File "/usr/lib/python2.7/ssl.py", line 241, in recv
    return self.read(buflen)
  File "/usr/lib/python2.7/ssl.py", line 160, in read
    return self._sslobj.read(len)
error: [Errno 104] Connection reset by peer
Storing debug log for failure in /root/.pip/pip.log
FATAL: all hosts have already failed -- aborting